Compressible Knee Prosthesis Augment for Asymmetric Bone Fit
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Solution Overview
Problem
Existing augment elements for prostheses, such as those for the tibia and femur, fail to precisely match the asymmetric bone anatomy of patients, leading to unsatisfactory performance and increased surgical complexity during insertion and removal.
Innovation Solution
An augment element with a metal body of a substantially truncated conical shape, featuring an eccentrically stacked axial cavity and a metal trabecular surface, designed to adapt to specific bone anatomy, including through-slits for radial compression, enhancing press-fit and osseointegration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a conventional symmetric augment element is used, then the device complexity is reduced, but the adaptability to asymmetric bone anatomy deteriorates
Solution Approach 1:
The patent applies asymmetry by designing the augment element with an asymmetric external configuration that specifically matches the asymmetric anatomy of tibial and femoral bones. The augment element features different dimensions and shapes at its proximal and distal ends, allowing it to conform to the specific anatomical variations of patient bones, thereby improving adaptability while maintaining manageable device complexity through purposeful asymmetric design rather than complex adjustable mechanisms
2Adaptability or versatility
If a conventional augment element with uniform cross-section is used, then the manufacturing precision is improved, but the adaptability to specific bone anatomy deteriorates
Solution Approach 1:
The patent applies segmentation by dividing the augment element into multiple cross-sections along its longitudinal axis, where each cross-section has different geometric characteristics. This segmentation allows each portion of the augment element to be tailored to specific anatomical regions of the bone, improving adaptability while maintaining manufacturing precision through standardized segment geometries that can be produced with conventional precision manufacturing techniques
3Ease of operation
If a solid metal augment element is used, then the strength is improved, but the ease of operation during insertion deteriorates
Solution Approach 1:
The patent applies dynamics by designing the augment element with collapsible walls that can change their configuration during insertion. The walls are configured to be flexible during the insertion process, allowing the augment element to compress and pass through the bone more easily, while maintaining structural strength once implanted and loaded. This dynamic behavior resolves the contradiction between ease of insertion and structural strength
4Reliability
If a smooth surface augment element is used, then the ease of manufacture is improved, but the reliability of bone attachment deteriorates
Solution Approach 1:
The patent applies porous materials by incorporating a porous surface structure on the external surface of the augment element. This porous structure increases the surface area available for bone ingrowth and attachment, improving the reliability of bone integration. The porous structure can be manufactured using established techniques such as foam metallurgy or additive manufacturing, maintaining reasonable ease of manufacture while significantly enhancing bone attachment reliability
Data Source
AI summary
Augment element for knee prosthesis, comprising a metal body of a substantially truncated conical shape configured to be inserted into a bone extremity and having an outer surface comprising a metal trabecular surface. The metal body being hollow with an axial through-cavity defining a plurality of substantially annular transversal sections. The metal body is inclined in a direction of inclination, so as to define at least one eccentricity between a first transversal section at a first end of the axial through-cavity and a second transversal section at a second end of the axial through-cavity. The augment element further comprises a plurality of through-slits in the metal body, open from the first end up to an intermediate portion on the metal body, wherein the plurality of through-slits is configured for a radial compression of the metal body, locally reducing a circumference of the substantially annular transversal sections during insertion of the augment element, and increasing a press-fit towards a bone portion.